Generally, joints in a hydraulic excavator, which is a type of construction equipment, and arm supporting joints in a crane, which is also a type of construction equipment, have a structure in which a shaft inserted in bearings can be repeatedly and relatively swung within a fixed rotation angle, and a high surface pressure of 60 MPa or more can be received. Therefore, as this type of bearing assembly, a sliding bearing assembly using material having superior abrasion resistance can be used, and it is used by interposing lubricating oil, grease, wax, etc., having a high viscosity between sliding surfaces thereof. In such a sliding bearing assembly, it is necessary to sufficiently supply lubricating oil to the sliding surfaces, and as a result, a smooth bearing action can be obtained by preventing metallic contact to avoid abrasion, even if it is used under a high surface pressure. Therefore, a bush for the sliding bearing assembly is made of materials such as heat-treated carbon steel, high strength brass, etc., and in recent years, sintered material containing 10 to 30 weight % of Cu can be specifically used, for example, as described in Patent Publication 1.
The Patent Publication 1 is Japanese Unexamined Patent Application Publication No. Hei 11-117940.